It's a classic scene in a movie. I am facing an enemy within arms reach. The two of us are at a standoff, guns pointed at one another's heads at point blank range.

In the movies, the two of us slowly, slowly back off, then simultaneously dive for cover and resume our shotoff at a later date.

However, it seems to me that the easier thing to do is pull the trigger. Here's where the factual question comes in:

If shot in the face, is there any way my opponent shoots back? Are human reflexes fast enough to pull the trigger in the split second between my finger twitching and the bullet enters his brain? Could getting shot in the head make his hand clench reflexively in a way that would fire a weapon?

Or would I in all likelihood walk away with not more damage than a brain-splattered coat?

Well you would have to be more specific than just the face or brain. Humans have lived with bullets in/through their brain - and some suicide victims have shot themselves in the head multiple times.

In theory - I have read that if you hit the brain stem - there is no chance that the person will fire the gun, that all control is severed. If that is true - I don't think reaction time will be an issue.

You'd of course have to be (or would want to be) 100% sure you can hit whatever zone is required to cause this instant capacitation. Or actually maybe not 100% sure as from a game theory perspective - it seems like it would be a bad idea to risk being on the other side of a shot. But if you want to avoid this situation - you'd probably want to know the right place to aim...

Driver's Ed said 2/10ths of a second for your brain to decipher what your eye sends (in that case, the brake lights of the car you're tailgating).

If you are pointing a gun at my head, I will be watching your finger muscles REAL close, and will fire as soon as I see your metatarsals start to contract. This means you need to pull trigger real fast - which generally causes you to twist your wrist, throwing off your aim.

Maybe you should just back off slowly while keeping both hands in firing position and a sharp eye on finger muscles.